Field of the Invention
The present invention relates to a liquid-charged antivibration device used for an engine mount of a vehicle and the like.
Description of the Related Arts
Conventionally, as this kind of the liquid-charged antivibration device, a device disclosed in Patent Literature 1 (JP 2012-13153 A) is known. This liquid-charged antivibration device includes a first fitting member fitted to an engine, a second fitting member fitted to a vehicle body, and an insulator for connecting the first fitting member and the second fitting member. In this liquid-charged antivibration device, an operating liquid is housed inside the insulator, and the inside of the insulator is partitioned in a main liquid chamber and a sub liquid chamber by a partitioning member.
The partitioning member sandwiches and holds an elastic movable membrane at the central portion thereof by an upper plate and a lower holder, which are separated in upper and lower, and is provided with an orifice passage on the outside in the radial direction of the elastic movable membrane. The elastic movable membrane communicates with the main liquid chamber and the sub liquid chamber through the central upper opening of the upper plate and the central lower opening of the lower holder. The elastic movable membrane is elastically deformed by variation of the liquid pressure in the main liquid chamber, and thereby absorbs the variation in the internal pressure.
The dynamic characteristics of this liquid-charged antivibration device change depending on the shape and the dimensions (cross-sectional area and the length) of the orifice passage at the time when the operating liquid flows, and the characteristics (density and viscosity) of the operating liquid. In addition, it is known that the above dynamic characteristics depend on an input amplitude condition (i.e., have amplitude dependency).
In general, in a liquid-charged antivibration device, if the input amplitude at the time of idling or the like is relatively small, low dynamic spring characteristic is required. On the other hand, if the input amplitude at the time of engine shake or the like is relatively large, high damping characteristic is required.